The present invention relates to a method and apparatus for correcting transparent defects on a photomask.
There has been used a lift-off method for correcting transparent defects on the photomask. The lift-off method includes the following steps, and it is disadvantageous that the method needs so many steps and takes long time.
(1) A step of applying photoresist to the entire surface of a photomask which includes the transparent defects.
(2) A step of exposing only the transparent defect portion to light using a partial exposure method.
(3) A step of opening a window in the resist at the transparent defect portion by a process of development.
(4) A step of forming a metallic film over the transparent defect portion and its periphery or over the entire surface of the photomask.
(5) A step of removing the resist and, at the same time, removing the metallic film formed on the resist.
There has also been proposed a method of partial deposition using laser, however, it has many practical problems concerning the accuracy, strength of the film and uniformity of the film.